Polyether-functionalized redox shuttle additives for lithium ion batteries

ABSTRACT

Compounds may have general Formula I, II, or III: 
     
       
         
         
             
             
         
       
     
     where R 1 , R 2 , R 3 , and R 4  are independently H, F, Cl, Br, CN, NO 2 , a alkyl group, a haloalkyl group, a phosphate group, a polyether group; or R 1  and R 2 , or R 3  and R 4 , or R 2  and R 3  (in the case of Formula II) may join together to form a fused ring on the benzene ring; and X and Z are independently a group of Formula A: 
     
       
         
         
             
             
         
       
     
     where R 5  and R 6  and R 7  are independently H, F, Cl, Br, CN, NO 2 , a alkyl group, a haloalkyl group, a phosphate group, or a polyether group; R 7  is H, F, Cl, Br, CN, NO 2 , a alkyl group, a haloalkyl group, a phosphate group, or a polyether group; n is an integer from 1 to 8; and m is an integer from 1 to 13. Such compounds may be used as redox shuttles in electrolytes for use in electrochemical cells, batteries and electronic devices.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of U.S. Provisional PatentApplication 61/348,063, filed on May 25, 2010, the entire contents ofwhich are incorporated herein by reference, for any and all purposes.

GOVERNMENT INTERESTS

This invention was made with Government support under Contract No.W-31-109-ENG-38 awarded by the Department of Energy. The Government hascertain rights in this invention.

FIELD

The present technology relates generally to the electrolyte redoxshuttle compounds carried in the non-aqueous electrolyte providingintrinsic overcharge protection capability for lithium ion batteries,electrical double-layer capacitors and other electrochemical devices.

BACKGROUND

Lithium ion batteries were first commercialized in 1990, and soonthereafter drew tremendous attention from academic and industryinterests due to the advantages such as high energy density and rapidcharge/discharge capabilities in comparison to state of the batterytechnology at the time. In recent years, lithium ion battery technologyhas become the most popular power source for portable electronicdevices. In addition, lithium ion batteries have found application inhybrid electric vehicles (HEV) and plug-in hybrid electric vehicles(PHEV). However, safety of lithium batteries continues to plague thetechnology. For example, secondary lithium-ion batteries are known toexhibit problems in shorting of the battery, elevated operatingtemperatures and overcharge, which can lead to dangerous situations suchas overheating, fire, and explosion of the battery.

Overcharge occurs when electricity flow is forced through a cell whenits capacity is already full. This is one of the most common factorsthat could lead to serious safety issues of lithium-ion batteries. Dueto the manufacture processes, there is always a “weakest cell” in abattery pack (i.e. the cell with the lowest charging capability in amulti-cell battery pack). During charging, the weakest cell will reachfull capacity prior to the other cells, but because the overall voltageof the battery is not high, the full capacity cell with not trigger thevoltage monitor of the charger to read “full.” As a result, the weakestcell is put into an overcharge situation. Instead of being stored evenlyacross all electrodes in the battery pack, electricity will build up in,and increase the potential of, the cathode in the weakest cell, causingthe potential to go beyond the electrochemical window of theelectrolyte. In turn, this will cause reactions to occur such asoxidation of the electrolyte, leading up to and including explosion ofthe cell and battery pack.

Known methods to avoid the overcharge abuse in practice, include the useof electronic devices attached to each individual cell to monitor forovercharge, the use of overcharge protection compounds in each cell, andthe use of redox shuttles in the electrolyte of the electrochemicalcells.

A number of redox shuttle compounds are known. Generally, the redoxshuttle molecule can be reversibly oxidized and reduced at a definedpotential slightly higher than the end-of-charge potential of thepositive electrode. This mechanism can protect the cell from overchargeby locking the potential of the positive electrode at the oxidationpotential of the shuttle molecules.

For an ideal redox shuttle compound, there are at least three desirableproperties. The first property is that it should have a reversibleoxidation potential that is appropriate for the cathode material withwhich it is to be used. This means that the oxidation potential of theredox shuttle should be between 0.3V and 0.5V volts higher than theend-of-charge potential of the cathode. This will ensure that redoxshuttle is accessed only overcharge potentials. The second property isthat the redox shuttle should be electrochemically stabile orreversible. The stability and reversibility of the redox shuttle willdetermine how much overcharge protection is provided. The third propertyis that the redox shuttle is to have sufficient solubility in theelectrolyte system in order to have an effective amount of the redoxshuttle available.

SUMMARY

In one aspect, a compound of Formula I, II, or III is provided:

where R¹, R², R³, and R⁴ are independently H, F, Cl, Br, CN, NO₂, aalkyl group, a haloalkyl group, a phosphate group, a polyether group; orR¹ and R², or R³ and R⁴, or in the case of Formula II R² and R³ may jointogether to form a fused ring on the benzene ring; and X and Z areindependently a group of Formula A:

where R⁵ and R⁶ are independently H, F, Cl, Br, CN, NO₂, a alkyl group,a haloalkyl group, a phosphate group, or a polyether group; R⁷ is H, aalkyl group, a haloalkyl group, a phosphate group, or a polyether group;n is an integer from 1 to 8; and m is an integer from 1 to 13. In someembodiments, R¹, R², R³, and R⁴ are independently H, a alkyl group, ahaloalkyl group, or a polyether group. In some embodiments, R¹, R², R³,and R⁴ are independently H, a C₁-C₄ alkyl group, a C₁-C₄ haloalkylgroup, or a polyether group having from 2 to 20 carbon atoms. In someembodiments, R¹ and R⁴ are the same and are different from that of R²and R³. In some embodiments, R¹ and R⁴ are individually an alkyl groupor a haloalkyl group, and R² and R³ are hydrogen. In some embodiments,R¹ and R⁴ are individually methyl, ethyl, n-propyl, iso-propyl, n-butyl,sec-butyl, or tert-butyl and R² and R³ are H. In some embodiments, n is1 to 3. In some embodiments, m is from 1 to 6.

In some embodiments, R⁵ and R⁶ at each occurrence are individually H, aC₁-C₄ alkyl, a C₁-C₄ haloalkyl, H, Cl, Br, or I. In some embodiments, R⁵and R⁶ are H, methyl, ethyl, n-propyl, iso-propyl, n-butyl, sec-butyl,or tert-butyl. In some embodiments, R⁷ is H or an alkyl group. In someembodiments, R⁷ is H or a C₁-C₄ alkyl group. In some embodiments, R⁷ isH, methyl, ethyl, n-propyl, iso-propyl, n-butyl, sec-butyl, ortert-butyl. In some embodiments, n is 1 or 2. In some embodiments, n is2. In some embodiments, m is 1, 2, 3, or 4.

In some embodiments, the compound is that of Formula I; R¹, R², R³, andR⁴ are independently H, a C₁-C₄ alkyl group, a C₁-C₄ haloalkyl group, ora polyether group having from 2 to 20 carbon atoms; R⁵ and R⁶ at eachoccurrence are individually H, a C₁-C₄ alkyl, a C₁-C₄ haloalkyl, H, Cl,Br, or I; and R⁷ is H or an alkyl group. In some embodiments, thecompound is that of Formula I; R¹, R², R³, and R⁴ are independently H,methyl, ethyl, n-propyl, iso-propyl, n-butyl, sec-butyl, or tert-butyl,or a polyether group having from 2 to 20 carbon atoms; R⁵ and R⁶ at eachoccurrence are individually H or methyl; R⁷ is H, methyl, ethyl,n-propyl, iso-propyl, n-butyl, sec-butyl, or tert-butyl; and n is 1 or2. In some embodiments, the compound is that of Formula I; R¹ and R⁴ arethe same and are different from that of R² and R³; R⁵ and R⁶ at eachoccurrence are individually H, a C₁-C₄ alkyl, a C₁-C₄ haloalkyl, H, Cl,Br, or I; R⁷ is H or an alkyl group; and n is 1 or 2. In someembodiments, the compound is that of Formula I; R¹ and R⁴ areindividually an alkyl group or a haloalkyl group; R² and R³ arehydrogen; R⁵ and R⁶ at each occurrence are individually H or methyl; R⁷is H, methyl, ethyl, n-propyl, iso-propyl, n-butyl, sec-butyl, ortert-butyl; and n is 1 or 2. In some embodiments, the compound is thatof Formula I; R¹ and R⁴ are tert-butyl; R² and R³ are H; R⁵ and R⁶ ateach occurrence are individually H or methyl; R⁷ is H, methyl, or ethyl;and n is 1 or 2. In such embodiments, m is from 1 to 10. In other suchembodiments, m is from 1 to 6.

In some embodiments, the compound is1-nitro-3-tert-butyl-2,5-di-oligo(ethylene glycol)benzene;1-cyano-3-tert-butyl-2,5-di-oligo(ethylene glycol)benzene;1,4-di-tert-butyl-2,3-di-oligo(ethylene glycol)benzene;5-tert-butyl-1,3-dinitro-2,4-di-oligo(ethylene glycol)benzene;1-(benzyloxy)-4-bromo-2,3-di-oligo(ethylene glycol)benzene;1,3,5-tri-tert-butyl-2,4-di-oligo(ethylene glycol)benzene;2-methyl-1,4-di-oligo(ethylene glycol)benzene;2,3-dimethyl-1,4-di-oligo(ethylene glycol)benzene;2,5-dimethyl-1,4-di-oligo(ethylene glycol)benzene;2,6-dimethyl-1,4-di-oligo(ethylene glycol)benzene;2,3,6-trimethyl-1,2-di-oligo(ethylene glycol)benzene;2,3,5,6-tetramethyl-1,4-di-oligo(ethylene glycol)benzene;4-methyl-1,2-di-oligo(ethylene glycol)benzene;2,3,5,6-tetramethyl-1,4-di-oligo(ethylene glycol)benzene;2-ethyl-1,4-di-oligo(ethylene glycol)benzene;2,3-diethyl-1,4-di-oligo(ethylene glycol)benzene;2,5-diethyl-1,4-di-oligo(ethylene glycol)benzene;2,6-diethyl-1,4-di-oligo(ethylene glycol)benzene;2,3,6-triethyl-1,2-di-oligo(ethylene glycol)benzene;2,3,5,6-tetraethyl-1,4-di-oligo(ethylene glycol)benzene;4-ethyl-1,2-di-oligo(ethylene glycol)benzene;2,5-diisopropyl-1,4-di-oligo(ethylene glycol)benzene;2-tert-butyl-1,4-di-oligo(ethylene glycol)benzene;2,3-di-tert-butyl-1,4-di-oligo(ethylene glycol)benzene;2,5-di-tert-butyl-1,4-di-oligo(ethylene glycol)benzene;2,5-di-tert-pentyl-1,4-di-oligo(ethylene glycol)benzene;2,5-di-tert-butyl-3,6-di-nitro-1,4-di-oligo(ethylene glycol)benzene;2,5-di-tert-butyl-3,6-di-cyano-1,4-di-oligo(ethylene glycol)benzene;2,5-di-tert-butyl-1,4-di-oligo(ethylene glycol)benzene;2,5-dicyclohexyl-1,4-di-oligo(ethylene glycol)benzene;4-tert-butyl-1,2-di-oligo(ethylene glycol)benzene;4,5-di-tert-butyl-1,2-di-oligo(ethylene glycol)benzene;4,5-di-tert-pentyl-1,2-di-oligo(ethylene glycol)benzene;4,5-di-tert-butyl-1,2-diethoxybenzene; 9,10-di-oligo(ethyleneglycol)-1,4:5,8-dimethano-1,2,3,4,5,6,7,8-octahydroanthracene;9,10-di-oligo(ethyleneglycol)-1,4:5,8-diethano-1,2,3,4,5,6,7,8-octahydroanthracene;1,4-bis(2-methoxy)ethoxy-2,5-di-tert-butyl-benzene;1,4-bis(2-(2-methoxy)ethoxy)ethoxy-2,5-di-tert-butyl-benzene;1,4-bis(2-(2-(2-methoxy)ethoxy)ethoxy)ethoxy-2,5-di-tert-butyl-benzene;or1,4-bis(2-(2-(2-(2-methoxy)ethoxy)ethoxy)ethoxy)ethoxy-2,5-di-tert-butyl-benzene.

In some embodiments, the compound is1,4-bis(2-methoxy)ethoxy-2,5-di-tert-butyl-benzene;1,4-bis(2-(2-methoxy)ethoxy)ethoxy-2,5-di-tert-butyl-benzene;1,4-bis(2-(2-(2-methoxy)ethoxy)ethoxy)ethoxy-2,5-di-tert-butyl-benzene;or1,4-bis(2-(2-(2-(2-methoxy)ethoxy)ethoxy)ethoxy)ethoxy-2,5-di-tert-butyl-benzene.

In another aspect, an electrolyte is provided including an alkali metalsalt; a polar aprotic solvent; and a redox shuttle, where the redoxshuttle is any of compounds of Formula I, II, or III described abovegenerally, or specifically, and where the electrolyte solution issubstantially non-aqueous. In some embodiments, the redox shuttle has aredox potential of from 3 V to 5 V in the electrolyte. In someembodiments, the redox shuttle is present in the electrolyte from 0.0005wt % to 50 wt %. In some embodiments, the redox shuttle is present inthe electrolyte from 2 wt % to 10 wt %.

In some embodiments, the electrolyte also includes an electrodestabilizing compound that can be reduced or polymerized on the surfaceof a negative electrode to form a passivation film on the surface ofnegative electrode. In other embodiments, the electrolyte also includesan electrode stabilizing compound that can be oxidized or polymerized onthe surface of positive electrode to form a passivation film on thesurface of the positive electrode. In some embodiments, the electrodestabilizing compound is present from 0.001 wt % to 8 wt %.

In some embodiments, the alkali metal salt is other than Li[B(C₂O₄)₂] orLi[BF₂(C₂O₄)], and the electrolyte further includes an electrodestabilizing compound that is Li[B(C₂O₄)₂] or Li[BF₂(C₂O₄)]. In someembodiments, the electrode stabilizing compound is present from 0.001 wt% to 8 wt %.

In another aspect, an electrochemical device is provided including acathode; an anode; and an electrolyte including an alkali metal salt, apolar aprotic solvent, and a redox shuttle that is compound of FormulaI, II, or III, as described above, where the electrolyte solution issubstantially non-aqueous. In some embodiments, the device is a lithiumsecondary battery; the cathode is a lithium metal oxide cathode; theanode is a carbon, a lithium metal anode, or a lithium alloy; and theanode and cathode are separated from each other by a porous separator.In some embodiments, the cathode includes a spinel, a olivine, acarbon-coated olivine, LiFePO₄, LiCoO₂, LiNiO₂,LiNi_(1−x)Co_(y)Met_(z)O₂, LiMn_(0.5)Ni_(0.5)O₂,LiMn_(0.3)Co_(0.3)Ni_(0.3)O₂, LiMn₂O₄, LiFeO₂, LiMet_(0.5)Mn_(1.5)O₄,Li_(1+x′)Ni_(α)Mn_(β)Co_(γ)Met′_(δ)O_(2−z′)F_(z′), Nasicon,A_(n′)B₂(XO₄)₃, vanadium oxide, or mixtures of any two or more thereof,where Met is Al, Mg, Ti, B, Ga, Si, Mn, or Co; Met′ is Mg, Zn, Al, Ga,B, Zr, or Ti; A is Li, Ag, Cu, Na, Mn, Fe, Co, Ni, Cu, and Zn; B is Ti,V, Cr, Fe, and Zr; X is P, S, Si, W, Mo; 0≦x≦0.3, 0≦y≦0.5, 0≦z≦0.5,0≦m≦0.5 and 0≦n≦0.5; 0≦x′≦0.4, 0≦α≦1, 0≦β≦1, 0≦γ≦1, 0≦δ≦0.4, and0≦z′≦0.4; and 0≦n′≦3. In some embodiments, the cathode includes asurface coating of a metal oxide on particles of the cathode. In somesuch embodiments, the metal oxide includes ZrO₂, TiO₂, ZnO₂, WO₃, Al₂O₃,MgO, SiO₂, SnO₂ AlPO₄, or Al(OH)₃. In some embodiments, the anodeincludes graphite, amorphous carbon, Li₄Ti₅O₁₂, tin alloys, siliconalloys, intermetallic compounds, or lithium metal.

In another aspect, an electrochemical device is provided including aspinel, olivine, or carbon-coated olivine cathode; a graphite oramorphous carbon anode; and a substantially non-aqueous electrolyteincluding an alkali metal salt that is Li[BF₂(C₂O₄)] or Li[B(C₂O₄)₂], apolar aprotic solvent that is ethyl acetate; propyl acetate; ethylenecarbonate; propylene carbonate; dimethyl carbonate; diethyl carbonate;ethyl methyl carbonate; dimethyl ether; or γ-butyrolactone; a redoxshuttle that is any of the compounds of Formulas I, II, or III asdescribed above; and an electrode stabilizing compound that ispyridazine; vinyl pyridazine; quinoline; vinyl quinoline; pyridine;vinyl pyridine; indole; vinyl indole; triethanolamine; 1,3-dimethylbutadiene; butadiene; vinyl ethylene carbonate; vinyl carbonate;imidazole; vinyl imidazole; piperidine; vinyl piperidine; pyrimidine;vinyl pyrimidine; pyrazine; vinyl pyrazine; isoquinoline; vinylisoquinoline; quinoxaline; vinyl quinoxaline; biphenyl; 1,2-diphenylether; 1,2-diphenylethane; o-terphenyl; N-methylpyrrole; naphthalene;3,9-divinyl-2,4,8,10-tetraoxaspiro[5.5]undecane;3,9-divinyl-2,4,8-trioxaspiro[5.5]undecane;3,9-divinyl-2,4-dioxaspiro[5.5]undecane;3,9-diethylidene-2,4,8,10-tetraoxaspiro[5.5]undecane;3,9-diethylidene-2,4,8-trioxaspiro[5.5]undecane;3,9-diethylidene-2,4-dioxaspiro[5.5]undecane;3,9-dimethylene-2,4,8,10-tetraoxaspiro[5.5]undecane;3,9-divinyl-1,5,7,11-tetraoxaspiro[5.5]undecane;3,9-dimethylene-1,5,7,11-tetraoxaspiro[5.5]undecane; or3,9-diethylidene-1,5,7,11-tetraoxaspiro[5.5]undecane.

In another aspect, a method of preparing an electrolyte includescombining an alkali metal salt; a polar aprotic solvent; and a compoundof any of Formulas I, II, or III, as described above.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a series of cyclic voltammograms of1,4-bis(2-methoxyethoxy)-2,5-di-tert-butyl-benzene (10 mM) in 1.2 MLiPF₆ in EC/EMC (3:7 by weight) using a three electrode system, atdifferent scan rates.

FIG. 2 is a series of voltage profiles for a Li/LiFePO₄ cell containing0.1M 1,4-Bis(2-methoxyethoxy)-2,5-di-tert-butyl-benzene in 1.2M LiPF₆ inEC/EMC (3:7 by weight) during the course of 0 h to 3100 h at a chargingrate of C/10, and overcharge of 100%.

FIG. 3 is a capacity retention profile for a Li/LiFePO₄ cell containing0.1M 1,4-bis(2-methoxyethoxy)-2,5-di-tert-butyl-benzene in 1.2M LiPF₆ inEC/EMC (3:7 by weight) during the course of 0 h to 3100 h at a chargingrate of C/10, and overcharge is 100%.

FIG. 4 is a series of voltage profiles for a MCMB/LiFePO₄ cellcontaining 0.1M 1,4-bis(2-methoxyethoxy)-2,5-di-tert-butyl-benzene in1.2M LiPF₆ in EC/EMC (3:7 by weight) during the course of 0 h to 3100 hat a charging rate of C/10, and overcharge is 100%.

FIG. 5 is a capacity retention profile for a MCMB/LiFePO₄ cellcontaining 0.1M 1,4-bis(2-methoxyethoxy)-2,5-di-tert-butyl-benzene in1.2M LiPF₆ in EC/EMC (3:7 by weight) during the course of 0 h to 3100 h,at a charging rate of C/10, and overcharge is 100%.

FIG. 6 is a series of voltage profiles for a LTO/LiFePO₄ cell containing0.1M 1,4-bis(2-methoxyethoxy)-2,5-di-tert-butyl-benzene in 1.2M LiPF₆ inEC/EMC (3:7 by weight) during the course of 0 h to 3100 h at a chargingrate of C/10, and overcharge is 100%.

FIG. 7 is a capacity retention profile for a LTO/LiFePO₄ cell containing0.1M 1,4-bis(2-methoxyethoxy)-2,5-di-tert-butyl-benzene in 1.2M LiPF₆ inEC/EMC (3:7 by weight) during the course of 0 h to 3100 h, at a chargingrate of C/10, and overcharge is 100%.

FIG. 8 is a series of voltage profiles for a MCMB/LiFePO₄ cellcontaining 0.2 M 1,4-bis(2-methoxyethoxy)-2,5-di-tert-butyl-benzene in1.2M LiPF₆ in EC/EMC (3:7 by weight) during the course of 0 h to 3100 hat a charging rate of C/5, and overcharge is 100%.

FIG. 9 is a capacity retention profile for a MCMB/LiFePO₄ cellcontaining 0.2 M 1,4-bis(2-methoxyethoxy)-2,5-di-tert-butyl-benzene in1.2M LiPF₆ in EC/EMC (3:7 by weight) during the course of 0 h to 3100 h,at a charging rate of C/5, and overcharge is 100%.

FIG. 10 is a series of voltage profiles for a MCMB/LiFePO₄ cellcontaining 0.4 M 1,4-bis(2-methoxyethoxy)-2,5-di-tert-butyl-benzene in1.2M LiPF₆ in EC/EMC (3:7 by weight) during the course of 0 h to 3100 hat a charging rate of C/2, and overcharge is 100%.

FIG. 11 is a capacity retention profile for a MCMB/LiFePO₄ cellcontaining 0.4 M 1,4-bis(2-methoxyethoxy)-2,5-di-tert-butyl-benzene in1.2M LiPF₆ in EC/EMC (3:7 by weight) during the course of 0 h to 3100 h,at a charging rate of C/2, and overcharge is 100%.

DETAILED DESCRIPTION

In one aspect, compounds having at least one aromatic ring with two ormore polyether or poly(ethylene oxide) (PEO) groups bonded through anoxygen to the aromatic ring are provided. Such compounds may be employedin a variety of applications. For example, in some embodiments, thecompounds are redox shuttles that are capable of providing overchargeprotection to an electrochemical cell and which exhibit sufficientsolubility in carbonate-based electrolytes to allow for dissolution ofthe compounds sat acceptable levels.

According to one embodiment, the compound has Formula I, II, or III:

In such compounds, R¹, R², R³, and R⁴ are independently H, F, Cl, Br,CN, NO₂, a alkyl group, a haloalkyl group, a phosphate group, apolyether group; or R¹ and R², or R³ and R⁴, or in the case of FormulaII R² and R³ also may join together to form a fused ring on the benzenering; and X and Z are independently a group of Formula A:

In the group of Formula A, R⁵ and R⁶ are independently H, F, Cl, Br, CN,NO₂, a alkyl group, a haloalkyl group, a phosphate group, or a polyethergroup; R⁷ is H, a alkyl group, a haloalkyl group, a phosphate group, ora polyether group; n is an integer from 1 to 8; and m is an integer from1 to 13. As used herein, the CR⁵R⁶ may be repeated n times, and in eachindividual unit, R⁵ and R⁶ are independently selected as indicatedabove. In some embodiments, R⁵ and R⁶ are H. In other embodiments, R⁵and R⁶ at each occurrence are individually H, a C₁-C₄ alkyl, a C₁-C₄haloalkyl, H, Cl, Br, or I. In yet other embodiments, R⁵ and R⁶ at eachoccurrence are individually H, methyl, ethyl, n-propyl, iso-propyl,n-butyl, sec-butyl, or tert-butyl. In some embodiments, R⁷ is H or analkyl group. In other embodiments, R⁷ is H or a C₁-C₄ alkyl group. Insome embodiments, R⁷ is H, methyl, ethyl, n-propyl, iso-propyl, n-butyl,sec-butyl, or tert-butyl. In some embodiments, n is 1 to 3. In someembodiments, m is from 1 to 6.

In some embodiments, R¹, R², R³, and R⁴ are independently H, a alkylgroup, a haloalkyl group, or a polyether group. In other embodiments,R¹, R², R³, and R⁴ are independently H, a C₁-C₄ alkyl group, a C₁-C₄haloalkyl group, or a polyether group having from 2 to 20 carbon atoms.In some embodiments, R¹ and R⁴ are the same and are different from thatof R² and R³. In some embodiments, R¹ and R⁴ are individually an alkylgroup or a haloalkyl group, and R² and R³ are hydrogen. In someembodiments, R¹ and R⁴ are individually methyl, ethyl, n-propyl,iso-propyl, n-butyl, sec-butyl, or tert-butyl and R² and R³ are H. Inone embodiment, for any of the compounds of Formula I, II, or III, atleast one of R¹, R², R³, and R⁴ is other than H.

In some embodiments, R¹ and R⁴ are the same and are different from thatof R² and R³. In some embodiments, R¹ and R⁴ are individually an alkylgroup or a haloalkyl group, and R² and R³ are hydrogen. In someembodiments, R¹ and R⁴ are individually methyl, ethyl, n-propyl,iso-propyl, n-butyl, sec-butyl, or tert-butyl and R² and R³ are H.

In some embodiments, the compound is that of Formula I; R¹, R², R³, andR⁴ are independently H, a C₁-C₄ alkyl group, a C₁-C₄ haloalkyl group, ora polyether group having from 2 to 20 carbon atoms; R⁵ and R⁶ at eachoccurrence are individually H, a C₁-C₄ alkyl, a C₁-C₄ haloalkyl, H, Cl,Br, or I; R⁷ is H or an alkyl group; n is 1 or 2; and m is from 1 to 8.In yet other embodiments, the compound is that of Formula I; R¹, R², R³,and R⁴ are independently H, methyl, ethyl, n-propyl, iso-propyl,n-butyl, sec-butyl, or tert-butyl, or a polyether group having from 2 to20 carbon atoms; R⁵ and R⁶ at each occurrence are individually H ormethyl; R⁷ is H, methyl, ethyl, n-propyl, iso-propyl, n-butyl,sec-butyl, or tert-butyl; n is 1 or 2; and m is from 1 to 8. In someembodiments, the compound is that of Formula I; R¹ and R⁴ are the sameand are different from that of R² and R³; R⁵ and R⁶ at each occurrenceare individually H, a C₁-C₄ alkyl, a C₁-C₄ haloalkyl, H, Cl, Br, or I;R⁷ is H or an alkyl group; n is 1 or 2; and m is from 1 to 8. In someembodiments, the compound is that of Formula I; R¹ and R⁴ areindividually an alkyl group or a haloalkyl group; R² and R³ arehydrogen; R⁵ and R⁶ at each occurrence are individually H or methyl; R⁷is H, methyl, ethyl, n-propyl, iso-propyl, n-butyl, sec-butyl, ortert-butyl; n is 1 or 2; and m is from 1 to 8. In some embodiments, thecompound is that of Formula I; R¹ and R⁴ are tert-butyl; R² and R³ areH; R⁵ and R⁶ at each occurrence are individually H or methyl; R⁷ is H,methyl, or ethyl; n is 1 or 2; and m is 1 to 4.

In other embodiments, the compound is an aromatic compound substitutedwith at least one tertiary carbon organic group and at least onepolyether group. Some compounds may contain two, or at least two,tertiary carbon organic groups which may be the same or different. Iflocated on the same aromatic ring (e.g., a benzene ring), the tertiarycarbon organic groups may be oriented ortho-, meta- or para- to oneanother. The polyether group may be a group of Formula A, as providedabove. In some embodiments, the polyether groups have from 1 to 13ethylene oxide (—CH₂CH₂O—) units. In other embodiments, the polyethergroups have from 1 to 10 ethylene oxide units. In other embodiments, thepolyether groups have from 2 to 6 ethylene oxide units. In otherembodiments, the polyether groups have from 1 to 4 ethylene oxide units.In other embodiments, the polyether groups have from 1 to 3 ethyleneoxide units. Some compounds may contain two or at least two polyethergroups which may be the same or different. If located on the samearomatic ring the polyether groups may for example be oriented ortho-,meta- or para- to one another.

In some embodiments, as described above, R¹ and R², or R³ and R⁴, or inthe case of Formula II R² and R³ may join together to form a fused ringon the benzene ring. The compound may include from 1 to 3 aromatic ringsthat are fused or connected to the benzene ring. Each aromatic ring mayfor example be carbocyclic. Examples of such aromatic rings includebenzene, naphthalene, anthracene, biphenyl, and the like.

Such compounds include substituted di-oligo(ethylene glycol)benzenes,such as, 2-methyl-1,4-di-oligo(ethylene glycol)benzene,2,3-dimethyl-1,4-di-oligo(ethylene glycol)benzene,2,5-dimethyl-1,4-di-oligo(ethylene glycol)benzene,2,6-dimethyl-1,4-di-oligo(ethylene glycol)benzene,2,3,6-trimethyl-1,2-di-oligo(ethylene glycol)benzene,2,3,5,6-tetramethyl-1,4-di-oligo(ethylene glycol)benzene,4-methyl-1,2-di-oligo(ethylene glycol)benzene,2,3,5,6-tetramethyl-1,4-di-oligo(ethylene glycol)benzene,2-ethyl-1,4-di-oligo(ethylene glycol)benzene,2,3-diethyl-1,4-di-oligo(ethylene glycol)benzene,2,5-diethyl-1,4-di-oligo(ethylene glycol)benzene,2,6-diethyl-1,4-di-oligo(ethylene glycol)benzene,2,3,6-triethyl-1,2-di-oligo(ethylene glycol)benzene,2,3,5,6-tetraethyl-1,4-di-oligo(ethylene glycol)benzene,4-ethyl-1,2-di-oligo(ethylene glycol)benzene,2,5-diisopropyl-1,4-di-oligo(ethylene glycol)benzene,2-tert-butyl-1,4-di-oligo(ethylene glycol)benzene,2,3-di-tert-butyl-1,4-di-oligo(ethylene glycol)benzene,2,5-di-tert-butyl-1,4-di-oligo(ethylene glycol)benzene,2,5-di-tert-pentyl-1,4-di-oligo(ethylene glycol)benzene,2,5-di-tert-butyl-3,6-di-nitro-1,4-di-oligo(ethylene glycol)benzene,2,5-di-tert-butyl-3,6-di-cyano-1,4-di-oligo(ethylene glycol)benzene,2,5-di-tert-butyl-1,4-di-oligo(ethylene glycol)benzene,2,5-dicyclohexyl-1,4-di-oligo(ethylene glycol)benzene,4-tert-butyl-1,2-di-oligo(ethylene glycol)benzene,4,5-di-tert-butyl-1,2-di-oligo(ethylene glycol)benzene,4,5-di-tert-pentyl-1,2-di-oligo(ethylene glycol)benzene and4,5-di-tert-butyl-1,2-diethoxybenzene; substituted oligo(ethyleneglycol)naphthalenes, such as, 4,8-di-tert-butyl-1,5-di-oligo(ethyleneglycol)naphthalene; polycyclic compounds, such as,9,10-di-oligo(ethyleneglycol)-1,4:5,8-dimethano-1,2,3,4,5,6,7,8-octahydroanthracene and9,10-di-oligo(ethyleneglycol)-1,4:5,8-diethano-1,2,3,4,5,6,7,8-octahydroanthracene.

According to some embodiments, the compound is1,4-bis(2-methoxy)ethoxy-2,5-di-tert-butyl-benzene;1,4-bis(2-(2-methoxy)ethoxy)ethoxy-2,5-di-tert-butyl-benzene;1,4-bis(2-(2-(2-methoxy)ethoxy)ethoxy)ethoxy-2,5-di-tert-butyl-benzene;or1,4-bis(2-(2-(2-(2-methoxy)ethoxy)ethoxy)ethoxy)ethoxy-2,5-di-tert-butyl-benzene.

In another aspect, the above compounds are employed as redox shuttles inan electrolyte. According to one embodiment, the redox shuttle is acompound of Formula I, II, or III, as described above. In otherembodiments, the redox shuttle is a compound of Formula I, as describedabove. Such compounds have been determined to have good compatibilitywith carbonate-based electrolytes. Such electrolytes, employing thecompounds as redox shuttles, provide overcharge protection tolithium-ion batteries.

According to one embodiment, the redox shuttle has Formula I, II, orIII:

In such redox shuttles, R¹, R², R³, and R⁴ are independently H, F, Cl,Br, CN, NO₂, a alkyl group, a haloalkyl group, a phosphate group, apolyether group; or R¹ and R², or R³ and R⁴, or in the case of FormulaII R² and R³ also may join together to form a fused ring on the benzenering; and X and Z are independently a group of Formula A:

In the group of Formula A, R⁵ and R⁶ are independently H, F, Cl, Br, CN,NO₂, a alkyl group, a haloalkyl group, a phosphate group, or a polyethergroup; R⁷ is H, a alkyl group, a haloalkyl group, a phosphate group, ora polyether group; n is an integer from 1 to 8; and m is an integer from1 to 13. As used herein, the CR⁵R⁶ may be repeated n times, and in eachindividual unit, R⁵ and R⁶ are independently selected as indicatedabove. In some embodiments, R⁵ and R⁶ are H. In other embodiments, R⁵and R⁶ at each occurrence are individually H, a C₁-C₄ alkyl, a C₁-C₄haloalkyl, H, Cl, Br, or I. In yet other embodiments, R⁵ and R⁶ at eachoccurrence are individually H, methyl, ethyl, n-propyl, iso-propyl,n-butyl, sec-butyl, or tert-butyl. In some embodiments, R⁷ is H or analkyl group. In other embodiments, R⁷ is H or a C₁-C₄ alkyl group. Insome embodiments, R⁷ is H, methyl, ethyl, n-propyl, iso-propyl, n-butyl,sec-butyl, or tert-butyl. In some embodiments, n is 1 to 2. In someembodiments, m is from 1 to 4.

In some embodiments, R¹, R², R³, and R⁴ are independently H, a alkylgroup, a haloalkyl group, or a polyether group. In other embodiments,R¹, R², R³, and R⁴ are independently H, a C₁-C₄ alkyl group, a C₁-C₄haloalkyl group, or a polyether group having from 2 to 20 carbon atoms.In some embodiments, R¹ and R⁴ are the same and are different from thatof R² and R³. In some embodiments, R¹ and R⁴ are individually an alkylgroup or a haloalkyl group, and R² and R³ are hydrogen. In someembodiments, R¹ and R⁴ are individually methyl, ethyl, n-propyl,iso-propyl, n-butyl, sec-butyl, or tert-butyl and R² and R³ are H.

In some embodiments, R¹ and R⁴ are the same and are different from thatof R² and R³. In some embodiments, R¹ and R⁴ are individually an alkylgroup or a haloalkyl group, and R² and R³ are hydrogen. In someembodiments, R¹ and R⁴ are individually methyl, ethyl, n-propyl,iso-propyl, n-butyl, sec-butyl, or tert-butyl and R² and R³ are H.

In some embodiments, the redox shuttle is that of Formula I; R¹, R², R³,and R⁴ are independently H, a C₁-C₄ alkyl group, a C₁-C₄ haloalkylgroup, or a polyether group having from 2 to 20 carbon atoms; R⁵ and R⁶at each occurrence are individually H, a C₁-C₄ alkyl, a C₁-C₄ haloalkyl,H, Cl, Br, or I; R⁷ is H or an alkyl group; n is 1 or 2; and m is from 1to 8. In yet other embodiments, the redox shuttle is that of Formula I;R¹, R², R³, and R⁴ are independently H, methyl, ethyl, n-propyl,iso-propyl, n-butyl, sec-butyl, or tert-butyl, or a polyether grouphaving from 2 to 20 carbon atoms; R⁵ and R⁶ at each occurrence areindividually H or methyl; R⁷ is H, methyl, ethyl, n-propyl, iso-propyl,n-butyl, sec-butyl, or tert-butyl; n is 1 or 2; and m is from 1 to 8. Insome embodiments, the redox shuttle is that of Formula I; R¹ and R⁴ arethe same and are different from that of R² and R³; R⁵ and R⁶ at eachoccurrence are individually H, a C₁-C₄ alkyl, a C₁-C₄ haloalkyl, H, Cl,Br, or I; R⁷ is H or an alkyl group; n is 1 or 2; and m is from 1 to 8.In some embodiments, the redox shuttle is that of Formula I; R¹ and R⁴are individually an alkyl group or a haloalkyl group; R² and R³ arehydrogen; R⁵ and R⁶ at each occurrence are individually H or methyl; R⁷is H, methyl, ethyl, n-propyl, iso-propyl, n-butyl, sec-butyl, ortert-butyl; n is 1 or 2; and m is from 1 to 8. In some embodiments, theredox shuttle is that of Formula I; R¹ and R⁴ are tert-butyl; R² and R³are H; R⁵ and R⁶ at each occurrence are individually H or methyl; R⁷ isH, methyl, or ethyl; n is 1 or 2; and m is 1 to 4.

In other embodiments, the redox shuttle is an aromatic redox shuttlesubstituted with at least one tertiary carbon organic group and at leastone polyether group. Some redox shuttles may contain two, or at leasttwo, tertiary carbon organic groups which may be the same or different.If located on the same aromatic ring (e.g., a benzene ring), thetertiary carbon organic groups may be oriented ortho-, meta- or para- toone another. The polyether group may be a group of Formula A, asprovided above. In some embodiments, the polyether groups have from 1 to13 ethylene oxide (—CH₂CH₂O—) units. In other embodiments, the polyethergroups have from 1 to 10 ethylene oxide units. In other embodiments, thepolyether groups have from 2 to 6 ethylene oxide units. In otherembodiments, the polyether groups have from 1 to 4 ethylene oxide units.In other embodiments, the polyether groups have from 1 to 3 ethyleneoxide units. Some compounds may contain two or at least two polyethergroups which may be the same or different. If located on the samearomatic ring the polyether groups may for example be oriented ortho-,meta- or para- to one another.

In some embodiments, as described above, R¹ and R², or R³ and R⁴, or inthe case of Formula II R² and R³ may join together to form a fused ringon the benzene ring. The redox shuttle may include from 1 to 3 aromaticrings that are fused or connected to the benzene ring. Each aromaticring may for example be carbocyclic. Examples of such aromatic ringsinclude benzene, naphthalene, anthracene, biphenyl, and the like. Othersubstituents may be present on the shuttle aromatic ring or rings or onthe tertiary carbon organic group(s) or alkoxy group(s), so long as suchsubstituents do not unduly interfere with factors such as the shuttle'scharge-carrying capability, oxidation potential or stability.

Such redox shuttles include, substituted di-oligo(ethyleneglycol)benzenes, such as, 2-methyl-1,4-di-oligo(ethylene glycol)benzene,2,3-dimethyl-1,4-di-oligo(ethylene glycol)benzene,2,5-dimethyl-1,4-di-oligo(ethylene glycol)benzene,2,6-dimethyl-1,4-di-oligo(ethylene glycol)benzene,2,3,6-trimethyl-1,2-di-oligo(ethylene glycol)benzene,2,3,5,6-tetramethyl-1,4-di-oligo(ethylene glycol)benzene,4-methyl-1,2-di-oligo(ethylene glycol)benzene,2,3,5,6-tetramethyl-1,4-di-oligo(ethylene glycol)benzene,2-ethyl-1,4-di-oligo(ethylene glycol)benzene,2,3-diethyl-1,4-di-oligo(ethylene glycol)benzene,2,5-diethyl-1,4-di-oligo(ethylene glycol)benzene,2,6-diethyl-1,4-di-oligo(ethylene glycol)benzene,2,3,6-triethyl-1,2-di-oligo(ethylene glycol)benzene,2,3,5,6-tetraethyl-1,4-di-oligo(ethylene glycol)benzene,4-ethyl-1,2-di-oligo(ethylene glycol)benzene,2,5-diisopropyl-1,4-di-oligo(ethylene glycol)benzene,2-tert-butyl-1,4-di-oligo(ethylene glycol)benzene,2,3-di-tert-butyl-1,4-di-oligo(ethylene glycol)benzene,2,5-di-tert-butyl-1,4-di-oligo(ethylene glycol)benzene,2,5-di-tert-pentyl-1,4-di-oligo(ethylene glycol)benzene,2,5-di-tert-butyl-3,6-di-nitro-1,4-di-oligo(ethylene glycol)benzene,2,5-di-tert-butyl-3,6-di-cyano-1,4-di-oligo(ethylene glycol)benzene,2,5-di-tert-butyl-1,4-di-oligo(ethylene glycol)benzene,2,5-dicyclohexyl-1,4-di-oligo(ethylene glycol)benzene,4-tert-butyl-1,2-di-oligo(ethylene glycol)benzene,4,5-di-tert-butyl-1,2-di-oligo(ethylene glycol)benzene,4,5-di-tert-pentyl-1,2-di-oligo(ethylene glycol)benzene and4,5-di-tert-butyl-1,2-diethoxybenzene; substituted oligo(ethyleneglycol)naphthalenes, such as, 4,8-di-tert-butyl-1,5-di-oligo(ethyleneglycol)naphthalene; polycyclic compounds, such as,9,10-di-oligo(ethyleneglycol)-1,4:5,8-dimethano-1,2,3,4,5,6,7,8-octahydroanthracene and9,10-di-oligo(ethyleneglycol)-1,4:5,8-diethano-1,2,3,4,5,6,7,8-octahydroanthracene.

According to some embodiments, the redox shuttle is1,4-bis(2-methoxy)ethoxy-2,5-di-tert-butyl-benzene;1,4-bis(2-(2-methoxy)ethoxy)ethoxy-2,5-di-tert-butyl-benzene;1,4-bis(2-(2-(2-methoxy)ethoxy)ethoxy)ethoxy-2,5-di-tert-butyl-benzene;or1,4-bis(2-(2-(2-(2-methoxy)ethoxy)ethoxy)ethoxy)ethoxy-2,5-di-tert-butyl-benzene.

The redox shuttles operate in an electrochemical range defined by thecharacteristics of the positive electrode and which can provideover-discharge protection in series-connected cells. A negativeelectrode having a larger irreversible first cycle capacity loss thanthat of the positive electrode is employed, so that if a cell is driveninto reversal. the potential of the negative electrode is driven abovethat of the positive electrode. During over-discharge, the potential ofthe negative electrode therefore increases. However, the shuttle limitsthe negative electrode potential to a value slightly above that of thepositive electrode maximum normal operating potential and prevents thenegative electrode from reaching even higher and more destructivepotentials. A negative electrode current collector whose lithiumalloying potential is below the negative electrode minimum normaloperating potential is also employed. This prevents the currentcollector from capturing lithium during recharging of the Li-ion cell.The resulting battery chemically limits or eliminates cell damage due torepeated over-discharge even though the negative electrode in a weakcell may be driven to a value more positive than the positive electrodepotential.

A variety of redox shuttles may be employed in lithium-ion batteries.Suitable redox shuttles have an electrochemical potential above (e.g.,slightly above) the positive electrode's maximum normal operatingpotential. Thus, according to some embodiments, redox shuttles in theelectrolytes, have a redox potential from 3.5 V to 5.0 V. In otherembodiments, the redox shuttles have a redox potential from 3.6 V to 4.6V.

The redox shuttle selection may be guided in part by the positiveelectrode selection. As a general numeric guide, the shuttle may have aredox potential from 0.3 V to 0.6 V above the positive electrode'smaximum normal operating potential, e.g., from 3.7 to 4.7 V vs. Li/Li⁺,from 3.7 V to 4.4 V vs. Li/Li⁺, from 3.7 V to 4.2 V vs. Li/Li⁺, or from3.7 V to 4.0 V vs. Li/Li⁺ above the positive electrode's maximum normaloperating potential. For example, LiFePO₄ positive electrodes have arecharge plateau of around 3.45 V vs. Li/Li⁺, and redox shuttles for usewith such electrodes may have a redox potential from 3.75 V to about4.05 V vs. Li/Li⁺. Similarly, LiMnPO₄ and LiMn₂O₄ electrodes have arecharge plateau around 4.1V vs. Li/Li⁺, and redox shuttles for use withsuch electrodes may have a redox potential from 4.4 V to 4.7 V vs.Li/Li⁺.

Mixtures of two or more shuttles having different electrochemicalpotentials vs. Li/Li⁺ may also be employed. For example, a first shuttleoperative at 3.8V and a second shuttle operative at 3.9V may both beemployed in a single cell. If after many charge/discharge cycles thefirst shuttle degrades and loses its effectiveness, the second shuttle(which would not meanwhile have been oxidized to form its radical cationwhile the first shuttle was operative) could take over and provide afurther (albeit higher potential) margin of safety against overcharge orover-discharge damage.

According to some embodiments, in addition to the redox shuttle, theelectrolyte includes a polar aprotic solvent, and a lithium metal salt.The electrolytes are substantially non-aqueous. As used herein,substantially non-aqueous means that the electrolytes do not containwater, or if water is present, it is only present at trace levels. Forexample, where the water is present at trace levels it is present atless than 20 ppm.

A variety of solvents may be employed in the electrolyte as the polaraprotic solvent. Suitable polar aprotic solvents include liquids andgels capable of solubilizing sufficient quantities of the lithium saltand the redox shuttle so that a suitable quantity of charge can betransported from the positive electrode to negative electrode. Thesolvents can be used over a wide temperature range, e.g., from −30° C.to 70° C. without freezing or boiling, and are stable in theelectrochemical range within which the cell electrodes and shuttleoperate. Suitable solvents include dimethyl carbonate; ethyl methylcarbonate; diethyl carbonate; methyl propyl carbonate; ethyl propylcarbonate; dipropyl carbonate; bis(trifluoroethyl) carbonate;bis(pentafluoropropyl) carbonate; trifluoroethyl methyl carbonate;pentafluoroethyl methyl carbonate; heptafluoropropyl methyl carbonate;perfluorobutyl methyl carbonate; trifluoroethyl ethyl carbonate;pentafluoroethyl ethyl carbonate; heptafluoropropyl ethyl carbonate;perfluorobutyl ethyl carbonate; fluorinated oligomers; dimethoxyethane;triglyme; dimethylvinylene carbonate; tetraethyleneglycol; dimethylether; polyethylene glycols; sulfones; and γ-butyrolactone.

The redox shuttles, as noted above, have suitable solubility incarbonate-based electrolyte solvents and gels. For example, the redoxshuttles may be prepared in carbonate-based electrolytes, such as, 1.2MLiPF₆ in EC/EMC 3/7 (i.e. an mixture of 3 parts ethylene carbonate and 7parts ethylmethylcarbonate), or 1.2M LiPF₆ in EC/DEC 5/5 (i.e. a 1:1mixture of ethylene carbonate and diethylcarbonate). According tovarious embodiments, electrolytes may be prepared with a redox shuttleat a concentration of from 0.005 wt % to 50 wt %, or from 0.1 wt % to 30wt %. In other embodiments, the electrolytes may be prepared with aredox shuttle at a concentration of from 2% to 10%.

Suitable lithium salts that may be used in the electrolytes, include,but are not limited to, Li[B(C₂O₄)₂]; Li[BF₂(C₂O₄)]; LiClO₄; LiBF₄;LiAsF₆; LiSbF₆; LiBr, LiPF₆; Li[CF₃SO₃]; Li[N(CF₃SO₂)₂]; Li[C(CF₃SO₂)₃];Li[B(C₆F₅)₄]; Li[B(C₆H₅)₄]; Li[N(SO₂CF₃)₂]; Li[N(SO₂CF₂CF₃)₂];LiN(SO₂C₂F₅)₂; Li[BF₃C₂F₅]; and Li[PF₃(CF₂CF₃)₃]; and lithium alkylfluorophosphates.

In some aspects, the electrolytes may include other additives to enhancethe performance of the electrolyte when used in an electrochemical cell.For example, the electrolytes may also include an electrode stabilizingcompound to protect the electrodes from degradation. Such electrodestabilizing compounds are described by co-pending U.S. patentapplication Ser. Nos. 10/857,365 and 11/279,120. Such electrodestabilizing compounds can be reduced or polymerized on the surface of anegative electrode to form a passivation film on the surface of thenegative electrode. Likewise, electrolytes can include an electrodestabilizing compound that can be oxidized or polymerized on the surfaceof the positive electrode to form a passivation film on the surface ofthe positive electrode. In some embodiments, the electrolytes furtherinclude mixtures of the two types of electrode stabilizing compounds.The compounds are typically present at a concentration of from 0.001 wt% to 8 wt %.

In some embodiments, the electrode stabilizing compound is a substitutedor unsubstituted linear, branched or cyclic hydrocarbon including atleast one oxygen atom and at least one aryl, alkenyl or alkynyl group.Passivating films may be formed from a substituted aryl compound or asubstituted or unsubstituted heteroaryl compound where the compoundincludes at least one oxygen atom. Alternatively, a combination of twocompounds may be used. In some embodiments, one compound is selectivefor forming a passivating film on the cathode to prevent leaching ofmetal ions and the other compound can be selective for passivating theanode surface to prevent or lessen the reduction of metal ions at theanode. Representative electrode stabilizing compounds include1,2-divinyl furoate, 1,3-butadiene carbonate, 1-vinylazetidin-2-one,1-vinylaziridin-2-one, 1-vinylpiperidin-2-one, 1 vinylpyrrolidin-2-one,2,4-divinyl-1,3-dioxane, 2 amino-3 vinylcyclohexanone,2-amino-3-vinylcyclopropanone, 2 amino-4-vinylcyclobutanone,2-amino-5-vinylcyclopentanone, 2-aryloxy-cyclopropanone,2-vinyl-[1,2]oxazetidine, 2 vinylaminocyclohexanol,2-vinylaminocyclopropanone, 2 vinyloxetane, 2-vinyloxy-cyclopropanone,3-(N-vinylamino)cyclohexanone, 3,5-divinyl furoate,3-vinylazetidin-2-one, 3 vinylaziridin 2 one, 3 vinylcyclobutanone, 3vinylcyclopentanone, 3 vinyloxaziridine, 3 vinyloxetane,3-vinylpyrrolidin-2-one, 4,4 divinyl-3 dioxolan 2-one, 4vinyltetrahydropyran, 5-vinylpiperidin-3-one, allylglycidyl ether,butadiene monoxide, butyl vinyl ether, dihydropyran-3-one, divinyl butylcarbonate, divinyl carbonate, divinyl crotonate, divinyl ether, divinylethylene carbonate, divinyl ethylene silicate, divinyl ethylene sulfate,divinyl ethylene sulfite, divinyl methoxypyrazine, divinylmethylphosphate, divinyl propylene carbonate, ethyl phosphate,methoxy-o-terphenyl, methyl phosphate, oxetan-2-yl-vinylamine,oxiranylvinylamine, vinyl carbonate, vinyl crotonate, vinylcyclopentanone, vinyl ethyl-2-furoate, vinyl ethylene carbonate, vinylethylene silicate, vinyl ethylene sulfate, vinyl ethylene sulfite, vinylmethacrylate, vinyl phosphate, vinyl-2-furoate, vinylcylopropanone,vinylethylene oxide, β-vinyl-γ-butyrolactone, or a mixture of any two ormore thereof. In some embodiments the electrode stabilizing compound maybe a cyclotriphosphazene that is substituted with F, alkyloxy,alkenyloxy, aryloxy, methoxy, allyloxy groups, or combinations thereof.For example, the compound may be a(divinyl)-(methoxy)(trifluoro)cyclotriphosphazene,(trivinyl)(difluoro)(methoxy)cyclotriphosphazene,(vinyl)(methoxy)(tetrafluoro)cyclotriphosphazene,(aryloxy)(tetrafluoro)(methoxy)-cyclotriphosphazene,(diaryloxy)(trifluoro)(methoxy)cyclotriphosphazene compounds, or amixture of two or more such compounds. In some embodiments, theelectrode stabilizing compound is vinyl ethylene carbonate, vinylcarbonate, or 1,2-diphenyl ether, or a mixture of any two or more suchcompounds.

Other representative electrode stabilizing compounds may includecompounds with phenyl, naphthyl, anthracenyl, pyrrolyl, oxazolyl,furanyl, indolyl, carbazolyl, imidazolyl, or thiophenyl groups. Forexample, electrode stabilizing compounds may be aryloxpyrrole, aryloxyethylene sulfate, aryloxy pyrazine, aryloxy-carbazole trivinylphosphate,aryloxy-ethyl-2-furoate, aryloxy-o-terphenyl, aryloxy-pyridazine,butyl-aryloxy-ether, divinyl diphenyl ether,(tetrahydro-furan-2-yl)-vinylamine, divinyl methoxybipyridine,methoxy-4-vinylbiphenyl, vinyl methoxy carbazole, vinyl methoxypiperidine, vinyl methoxypyrazine, vinyl methyl carbonate-allylanisole,vinyl pyridazine, 1-divinylimidazole, 3-vinyltetrahydrofuran, divinylfuran, divinyl methoxy furan, divinylpyrazine, vinyl methoxy imidazole,vinylmethoxy pyrrole, vinyl-tetrahydrofuran, 2,4-divinyl isooxazole, 3,4divinyl-1-methylpyrrole, aryloxyoxetane, aryloxy-phenyl carbonate,aryloxy-piperidine, aryloxy-tetrahydrofuran, 2-aryl-cyclopropanone,2-diaryloxy-furoate, 4-allylanisole, aryloxy-carbazole,aryloxy-2-furoate, aryloxy-crotonate, aryloxy-cyclobutane,aryloxy-cyclopentanone, aryloxy-cyclopropanone,aryloxy-cyclolophosphazene, aryloxy-ethylene silicate, aryloxy-ethylenesulfate, aryloxy-ethylene sulfite, aryloxy-imidazole,aryloxy-methacrylate, aryloxy-phosphate, aryloxy-pyrrole,aryloxyquinoline, diaryloxycyclotriphosphazene, diaryloxy ethylenecarbonate, diaryloxy furan, diaryloxy methyl phosphate, diaryloxy-butylcarbonate, diaryloxy-crotonate, diaryloxy-diphenyl ether,diaryloxy-ethyl silicate, diaryloxy-ethylene silicate,diaryloxy-ethylene sulfate, diaryloxyethylene sulfite, diaryloxy-phenylcarbonate, diaryloxy-propylene carbonate, diphenyl carbonate, diphenyldiaryloxy silicate, diphenyl divinyl silicate, diphenyl ether, diphenylsilicate, divinyl methoxydiphenyl ether, divinyl phenyl carbonate,methoxycarbazole, or 2,4-dimethyl-6-hydroxy-pyrimidine, vinylmethoxyquinoline, pyridazine, vinyl pyridazine, quinoline, vinylquinoline, pyridine, vinyl pyridine, indole, vinyl indole,triethanolamine, 1,3-dimethyl butadiene, butadiene, vinyl ethylenecarbonate, vinyl carbonate, imidazole, vinyl imidazole, piperidine,vinyl piperidine, pyrimidine, vinyl pyrimidine, pyrazine, vinylpyrazine, isoquinoline, vinyl isoquinoline, quinoxaline, vinylquinoxaline, biphenyl, 1,2-diphenyl ether, 1,2-diphenylethane, oterphenyl, N-methylpyrrole, naphthalene, or a mixture of any two or moresuch compounds.

In other embodiments, electrode stabilizing compounds includesubstituted or unsubstituted spirocyclic hydrocarbons containing atleast one oxygen atom and at least one alkenyl or alkynyl group. Forexample, such stabilizing compounds include those having Formula V:

where: D¹, D², D³, and D⁴ are independently O or CR²²R²³; provided thatD¹ is not O when G¹ is O, D² is not O when G² is O, D³ is not O when G³is O, and D⁴ is not O when G⁴ is O; G¹, G², G³, and G⁴ are independentlyO or CR²²R²³; provided that G¹ is not O when D¹ is O, G² is not O whenD² is O, G³ is not O when D³ is O, and G⁴ is not O when D⁴ is O; R²⁰ andR²¹ are independently a substituted or unsubstituted divalent alkenyl oralkynyl group; R²² and R²³ at each occurrence are independently H, F,Cl, a substituted or an unsubstituted alkyl, alkenyl, or alkynyl group.

Representative examples of Formula V include, but are not limited to,3,9 divinyl-2,4,8,10-tetraoxaspiro[5.5]undecane,3,9-divinyl-2,4,8-trioxaspiro[5.5]undecane,3,9-divinyl-2,4-dioxaspiro[5.5]undecane,3,9-diethylidene-2,4,8,10-tetraoxaspiro[5.5]undecane,3,9-diethylidene-2,4,8-trioxaspiro[5.5]undecane,3,9-diethylidene-2,4-dioxaspiro[5.5]undecane,3,9-dimethylene-2,4,8,10-tetraoxaspiro[5.5]undecane,3,9-divinyl-1,5,7,11-tetraoxaspiro[5.5]undecane, 3,9dimethylene-1,5,7,11-tetraoxaspiro[5.5]undecane,3,9-diethylidene-1,5,7,11-tetraoxaspiro[5.5]undecane, or a mixture ofany two or more such compounds. Furthermore, mixtures of any two or moreelectrode stabilizing compounds may also be used in the electrolytes.

In some embodiments, the electrode stabilizing compound is an anionreceptor. In some embodiments, the anion receptor is a Lewis acid. Inother embodiments, the anion receptor is a borane, a boronate, a borate,a borole, or a mixture of any two or more such compounds. In someembodiments, the anion receptor is a compound of the Formula VI:

where, each R¹⁷, R¹⁸, and R¹⁹ are independently halogen, alkyl, aryl,halogen-substituted alkyl, halogen-substituted aryl, or OR¹⁷; or any twoof R¹⁷, R¹⁸, and R¹⁹, together with the atoms to which they areattached, form a heterocyclic ring having 5-9 members, and R¹⁷ is ateach occurrence independently alkyl, aryl, halogen-substituted alkyl, orhalogen-substituted aryl.

In some embodiments, the anion receptors include, but not limited to,tri(propyl)borate, tris(1,1,1,3,3,3-hexafluoro-propan-2-yl)borate,tris(1,1,1,3,3,3-hexafluoro-2-phenyl-propan-2-yl)borate,tris(1,1,1,3,3,3-hexafluoro-2-(trifluoromethyl)propan-2-yl)borate,triphenyl borate, tris(4-fluorophenyl)borate,tris(2,4-difluorophenyl)borate, tris(2,3,5,6-tetrafluorophenyl)borate,tris(pentafluorophenyl)borate, tris(3-(trifluoromethyl)phenyl)borate,tris(3,5-bis(trifluoromethyl)phenyl)borate,tris(pentafluorophenyl)borane, or a mixture of any two or more thereof.Further suitable compounds include2-(2,4-difluorophenyl)-4-fluoro-1,3,2-benzodioxaborole,2-(3-trifluoromethyl phenyl)-4-fluoro-1,3,2-benzodioxaborole,2,5-bis(trifluoromethyl)phenyl-4-fluoro-1,3,2-benzodioxaborole,2-(4-fluorophenyl)-tetrafluoro-1,3,2-benzodioxaborole,2-(2,4-difluorophenyl)-tetrafluoro-1,3,2-benzodioxaborole,2-(pentafluorophenyl)-tetrafluoro-1,3,2-benzodioxaborole,2-(2-trifluoromethyl phenyl)-tetrafluoro-1,3,2-benzodioxaborole,2,5-bis(trifluoromethyl phenyl)-tetrafluoro-1,3,2-benzodioxaborole,2-phenyl-4,4,5,5-tetra(trifluoromethyl)-1,3,2-benzodioxaborolane,2-(3,5-difluorophenyl-4,4,5,5-tetrakis(trifluoromethyl)-1,3,2-dioxaborolane,2-(3,5-difluorophenyl-4,4,5,5-tetrakis(trifluoromethyl)-1,3,2-dioxaborolane,2-pentafluorophenyl-4,4,5,5-tetrakis(trifluoromethyl)-1,3,2-dioxaborolane,bis(1,1,1,3,3,3-hexafluoroisopropyl)phenyl-boronate,bis(1,1,1,3,3,3-hexafluoroisopropyl)-3,5-difluorophenylboronate,bis(1,1,1,3,3,3-hexafluoroisopropyl)pentafluorophenylboronate, or amixture of any two or more such compounds. In some embodiments, eachanion receptor is present at a concentration from 0.001 wt % to 10 wt %.

In some other embodiments, the electrolyte includes as an electrolytecompound, Li₂B₁₂X_(12−n)H_(n), Li₂B₁₀X_(10−n′)H_(n′), or a mixture oftwo or more of such compounds. Such electrolyte compounds may be presentfrom 0.001 wt % to 15 wt %. In such compounds, X is OH, OCH₃, F, Cl, Br,or I, n is an integer from 0 to 12, and n′ is an integer from 0 to 10.

In some embodiments, the electrolyte further includes a gel. Suchelectrolytes include a polar aprotic solvent; a lithium salt; a redoxshuttle; a crosslinking agent; monofunctional monomeric compound; and atleast one radical reaction initiator. In some embodiments, the gelelectrolyte can also include other electrode stabilization compounds andother electrolyte compounds. Suitable crosslinking agents may berepresented by Formula VII:

where R²⁰, R²¹, R²², and R²³ are each independently hydrogen, asubstituted or unsubstituted alkyl group having from 1 to 12 carbonatoms, or a substituted or unsubstituted alkenyl group having from 2 to12 carbon atoms; and where X′ is a hydrogen, methyl, or ethyl group, andn′″ is an integer from 1 to 15. Monofunctional monomeric compounds maybe used for the control of the crosslinking density of the gelelectrolyte. Suitable monofunctional monomeric compounds include thoseof Formula VIII:

where R²⁴ is an alkyl group having from 1 to 12 carbon atoms; R²⁵ andR²⁶ are each independently a hydrogen, a substituted or unsubstitutedalkyl group having from 1 to 12 carbon atoms, or a substituted orunsubstituted alkenyl group having from 2 to 12 carbon atoms; X′ ishydrogen, methyl or ethyl group; and q″ is an integer from 1 to 20.

Crosslinking agents and monofunctional monomeric compounds provide aphysical framework, or gel, after crosslinking to host the polar aproticsolvent. Variation of the amount of the crosslinking agent andmonofunctional monomeric compound in the gel may impact the conductivityof the gel electrolyte, due to changes in viscosity. Lower viscositygels are prepared with higher concentrations of monofunctional monomericcompound, as compared to the concentration of monofunctional monomericcompound used for higher viscosity gels. Without being bound by theory,higher viscosity gels may be expected to have lower electrochemicalconductivity, while lower viscosity gels may be expected to have higherelectrochemical conductivity. However, other electrochemical propertiesof the gel electrolyte, or an electrochemical cell prepared with the gelelectrolyte, such as oxidation potential and reduction potential, arenot expected to be impacted.

Polymerization of crosslinking agents and monofunctional monomericcompounds are known to those of skill in the art. For example,monofunctional monomeric compounds may be polymerized by thermal andphoto initiation. Representative thermal initiators include, but are notlimited to, an azo compound, a peroxide compound, bismaleimide, or amixture of any two or more thereof. One example of an azo compound isazoisobutyronitrile. One example of a peroxide compound isbenzoylperoxide. Representative photoinitiators include, but are notlimited to, 1-hydroxyl-phenyl-ketone, benzophenone,2-hydroxyl-2-methyl-1-phenyl-propanone,2-hydroxyl-1-[4-(2-hydroxy)phenyl]-2-methyl-1-propanone,methylbenzoylformate, oxy-phenyl-acetic acid2-[2-oxo-2-phenyl-acetoxy-ethoxy]-ethyl ester, oxy-phenyl-acetic2-[2-hydroxy-ethoxy]-ethyl ester, α,α-dimethoxy-α-phenylacetophenone,2-benzyl-2-(dimethylamino)-1-[4-(4-morpholinyl)phenyl]-1-propanone,diphenyl (2,4,6-trimethylthio)phenyl)-phosphine oxide, phosphine oxide,phenyl bis(2,4,6-trimethyl benzoyl), bis(η⁵-2,4-cyclopentadien-1-yl)bis[2,6-difluoro-3-(1H-pyrrol-1-yl)phenyl]titanium, iodonium(4-methylphenyl)-[4-(2-methylpropyl)phenyl]-hexafluorophosphate, or amixture of two or more thereof. In some instances the photoinitiator isa UV initiator.

In another aspect, a battery is provided including a plurality ofseries-connected rechargeable lithium ion cells. In such embodiments,each cell includes a negative electrode; a negative electrode currentcollector; a positive electrode; a positive electrode current collector;and an electrolyte as described above including the polar, aproticsolvent, the lithium salt, and the redox shuttle. In such systems thenegative electrode has a larger irreversible first cycle capacity lossthan that of the positive electrode, because the redox shuttle has anelectrochemical potential above the positive electrode maximum normaloperating potential, and the negative current collector has a lithiumalloying potential below the negative electrode minimum normal operatingpotential. In one embodiment, the electrode balance is adjusted (byusing a larger capacity negative electrode than positive electrode) sothat the redox shuttle can provide overcharge protection as well.

A variety of negative electrodes may be employed in lithium-ionbatteries. Representative negative electrodes include Li₄Ti₅O₁₂; thelithium alloy compositions described in U.S. Pat. Nos. 6,203,944;6,255,017; 6,436,578; 6,664,004; and 6,699,336; U.S. Patent ApplicationPublication Nos. 2003/0211390; 2004/013 1936; 2005/0031957; and2006/046144; graphitic carbons e.g., those having a spacing between(002) crystallographic planes, d₀₀₂, of 3.45 Å>d₀₀₂>3.354 Å and existingin forms such as powders, flakes, fibers or spheres (e.g., mesocarbonmicrobeads (MCMB)); other materials that will be familiar to thoseskilled in the art; and combinations thereof.

Where the negative electrode has a larger irreversible first cyclecapacity loss than that of the positive electrode, the positiveelectrode will normally remain at an elevated potential duringover-discharge. Its current collector will be held near the sameelevated potential and will not be susceptible to lithium capture duringrecharging or dissolution during over-discharging. Accordingly, thereare fewer constraints on selection of the positive electrode currentcollector. Representative positive electrode current collectors includealuminum, stainless steels (e.g., 300 series and 400 series stainlesssteels), titanium, tantalum, niobium, INCONEL alloys, combinationsthereof and other materials that will be familiar to those skilled inthe art. A variety of positive electrodes may be employed in lithium-ionbatteries in conjunction with the redox shuttles. Representativepositive electrodes include LiFePO₄, LiMnPO₄, LiMn₂O₄, LiCoPO₄, andLiCoO₂; lithium transition metal oxides as disclosed in U.S. Pat. Nos.5,858,324; 5,900,385; 6,143,268; 6,680,145; 6,964,828; 7,078,128; and7,211,237; U.S. Patent Application Publication Nos. 2003/0027048;2004/0121234; 2004/0 179993; and 2006/045144.

The negative or positive electrode may contain additives such as will befamiliar to those skilled in the art, e.g., carbon black for negativeelectrodes, and carbon black, flake graphite and the like for positiveelectrodes.

The negative and positive electrode capacities may optionally beselected to provide an excess negative electrode capacity. This enablesthe redox shuttle to provide overcharge protection. Ten percent totwenty percent excess negative electrode capacity is recommended. Lesseror greater excess negative electrode capacities may be employed ifdesired.

In another aspect, an electrical device is provided including anelectrical load (e.g., an electronic circuit, motor, illumination sourceor heat source) and the above-described battery. Exemplary embodimentsof the recited device can be made without electronic over-discharge (andoptionally without electronic overcharge) protection circuitry.

The following terms are used throughout as defined below.

The term “spinel” refers to manganese-based spinel such as, e.g.,Li_(1+x)Mn_(2−z)Met_(y)O_(4−m)X_(n), wherein Met is Al, Mg, Ti, B, Ga,Si, Ni, or Co; X is S or F; and wherein 0≦x≦0.3, 0≦y≦0.5, 0≦z≦0.5,0≦m≦0.5 and 0≦n≦0.5.

The term “olivine” refers to iron-based olivine such as, e.g.,LiFe_(1−z)Met″_(y)PO_(4−m)X_(n), wherein Met″ is Al, Mg, Ti, B, Ga, Si,Ni, Mn or Co; X is S or F; and wherein 0≦x≦0.3; 0≦y≦0.5, 0≦z≦0.5,0≦m≦0.5 and 0≦n≦0.5.

Alkyl groups include straight chain and branched alkyl groups havingfrom 1 to about 20 carbon atoms, and typically from 1 to 12 carbons or,in some embodiments, from 1 to 8 carbon atoms. As employed herein,“alkyl groups” include cycloalkyl groups as defined below. Examples ofstraight chain alkyl groups include methyl, ethyl, n-propyl, n-butyl,n-pentyl, n-hexyl, n-heptyl, and n-octyl groups. Examples of branchedalkyl groups include, but are not limited to, isopropyl, sec-butyl,t-butyl, neopentyl, and isopentyl groups. Representative substitutedalkyl groups may be substituted one or more times with, for example,amino, thio, hydroxy, cyano, alkoxy, and/or halo groups such as F, Cl,Br, and I groups. As used herein the term haloalkyl is an alkyl grouphaving one or more halo groups. In some embodiments, haloalkyl refers toa per-haloalkyl group.

Cycloalkyl groups are cyclic alkyl groups such as, but not limited to,cyclopropyl, cyclobutyl, cyclopentyl, cyclohexyl, cycloheptyl, andcyclooctyl groups. In some embodiments, the cycloalkyl group has 3 to 8ring members, whereas in other embodiments the number of ring carbonatoms range from 3 to 5, 6, or 7. Cycloalkyl groups further includepolycyclic cycloalkyl groups such as, but not limited to, norbornyl,adamantyl, bornyl, camphenyl, isocamphenyl, and carenyl groups, andfused rings such as, but not limited to, decalinyl, and the like.Cycloalkyl groups also include rings that are substituted with straightor branched chain alkyl groups as defined above. Representativesubstituted cycloalkyl groups may be mono-substituted or substitutedmore than once, such as, but not limited to: 2,2-; 2,3-; 2,4-; 2,5-; or2,6-disubstituted cyclohexyl groups or mono-, di-, or tri-substitutednorbornyl or cycloheptyl groups, which may be substituted with, forexample, alkyl, alkoxy, amino, thio, hydroxy, cyano, and/or halo groups.

Alkenyl groups are straight chain, branched or cyclic alkyl groupshaving 2 to about 20 carbon atoms, and further including at least onedouble bond. In some embodiments alkenyl groups have from 1 to 12carbons, or, typically, from 1 to 8 carbon atoms. Alkenyl groupsinclude, for instance, vinyl, propenyl, 2-butenyl, 3-butenyl,isobutenyl, cyclohexenyl, cyclopentenyl, cyclohexadienyl, butadienyl,pentadienyl, and hexadienyl groups among others. Alkenyl groups may besubstituted similarly to alkyl groups. Divalent alkenyl groups, i.e.,alkenyl groups with two points of attachment, include, but are notlimited to, CH—CH═CH₂, C═CH₂, or C═CHCH₃.

Alkynyl groups are straight chain or branched alkyl groups having 2 toabout 20 carbon atoms, and further including at least one triple bond.In some embodiments alkynyl groups have from 1 to 12 carbons, or,typically, from 1 to 8 carbon atoms. Exemplary alkynyl groups include,but are not limited to, ethynyl, propynyl, and butynyl groups. Alkynylgroups may be substituted similarly to alkyl groups. Divalent alkynylgroups, i.e., alkynyl groups with two points of attachment, include butare not limited to CH—C≡CH.

One skilled in the art will readily realize that all ranges discussedcan and do necessarily also describe all subranges therein for allpurposes, and that all such subranges also form part and parcel of thisdisclosure. Any listed range can be easily recognized as sufficientlydescribing and enabling the same range being broken down into at leastequal halves, thirds, quarters, fifths, tenths, etc. As a non-limitingexample, each range discussed herein can be readily broken down into alower third, middle third and upper third, etc.

All publications, patent applications, issued patents, and otherdocuments referred to in this specification are herein incorporated byreference as if each individual publication, patent application, issuedpatent, or other document was specifically and individually indicated tobe incorporated by reference in its entirety. Definitions that arecontained in text incorporated by reference are excluded to the extentthat they contradict definitions in this disclosure.

The present technology, thus generally described, will be understoodmore readily by reference to the following examples, which are providedby way of illustration and are not intended to be limiting.

EXAMPLES Example 1

Synthesis of 1,4-bis(2-methoxyethoxy)-2,5-di-tert-butyl-benzene. Scheme1 is an illustration of the synthesis of the title compound.

2,5-Di-tert-butylhydroquinone (0.2 mmol) was dissolved in anhydrous THF(20 ml). Sodium hydride (0.6 mmol) and 2-chloroethylethylether (0.4mmol) was then added to the solution. The reaction mixture was thenstirred at room temperature overnight. After removal of the solvent, theresidue was partitioned between dichloromethane and aqueous NaHCO₃(0.1M). The organic portion was separated and dried over Na₂SO₄. Aftersolvent removal in vacuo, the crude product was chromatographed (silica,hexanes/DCM from 5:1 to 1:1) to afford1,4-bis(2-methoxyethoxy)-2,5-di-tert-butyl-benzene in an 81% yield. Theproduct was characterized by ¹H NMR (300 MHz, CDCl₃, δ/ppm): 7.14 (s,2H), 4.11 (t, J=4.5 Hz, 4H), 3.80 (t, J=4.5 Hz, 4H), 3.45 (s, 6H), 1.37(s, 18H).

Example 2

Synthesis of1,4-bis[(2-methoxyethoxy)methoxy]-2,5-di-tert-butyl-benzene. The titlecompound was prepared in a manner similar to that of Example 1, bydissolving 2,5-Di-tert-butylhydroquinone (0.2 mmol) in anhydrous THF (20ml). Sodium hydride (0.6 mmol) and 2-methoxyethoxymethyl chloride (0.4mmol) was added to the solution. The reaction was stirred at roomtemperature overnight. After removal the solvent, the residue waspartitioned between dichloromethane and aqueous NaHCO₃ (0.1M). Theorganic portion was separated and dried over Na₂SO₄. After solventremoval in vacuo, the crude product was chromatographed (silica,hexanes/DCM from 5:1 to 1:1) to afford1,4-bis[(2-methoxyethoxy)methoxy]-2,5-di-tert-butyl-benzene in an 80%yield. The product was characterized by ¹H NMR (300 MHz, CDCl₃, δ/ppm):7.14 (s, 2H), 5.25 (s, 4H), 3.85 (t, J=4.5 Hz, 4H), 3.61 (t, J=4.5 Hz,4H), 3.40 (s, 6H), 1.36 (s, 18H).

Example 3

Cyclic voltammograms were recorded for a solution of1,4-bis(2-methoxyethoxy)-2,5-di-tert-butyl-benzene (10 mM) as a redoxshuttle in 1.2 M LiPF₆ in EC/EMC (3:7 by weight) using a three electrodesystem (Pt working electrode, Li counter electrode, and Li referenceelectrode) at different scan rates. See FIG. 1. One pair of reversiblepeaks is observed 3.8-4.1V vs. Li/Li⁺. The main electrolyte components(EC, PC, DMC, and LiPF₆) are electrochemically stable up to 4.8 V vs.Li/Li⁺, or higher. The reversible electrochemical reaction at 3.8-4.1 Vvs. Li/Li⁺ is thus assigned to the reduction and oxidation peaks for the1,4-bis(2-methoxyethoxy)-2,5-di-tert-butyl-benzene.

Example 4

Voltage profiles of a Li/LiFePO₄ cell containing 0.1M1,4-bis(2-methoxyethoxy)-2,5-di-tert-butyl-benzene as a redox shuttle in1.2M LiPF₆ in EC/EMC (3:7 by weight) were recorded over the course of 0h to 3100 h. See FIG. 2. The charging rate was at C/10 and theovercharge is 100%. The redox shuttle shows excellent overchargeprotection performance in the conventional carbonate-based electrolyte,and even at 0.1 M no solubility issues are observed.

Example 5

Capacity retention profiles of Li/LiFePO₄ cell containing 0.1 M1,4-Bis(2-methoxyethoxy)-2,5-di-tert-butyl-benzene in 1.2M LiPF₆ inEC/EMC (3:7 by weight) were recorded over the course of 0 h to 3100 h.See FIG. 3 The charging rate was at C/10 and the overcharge is 100%.After more than one hundred overcharge cycles, the cell performance inregards of capacity retention does exhibit an obvious decrease.

Example 6

Voltage profiles of a MCMB/LiFePO₄ cell containing 0.1 M1,4-bis(2-methoxyethoxy)-2,5-di-tert-butyl-benzene as a redox shuttle in1.2M LiPF₆ in EC/EMC (3:7 by weight) were recorded over the course of 0h to 3100 h. See FIG. 4. The charging rate was at C/10 and theovercharge is 100%. The overcharge protection resulted from theexemplary redox shuttle works well in the full cell with MCMB as theanode. As used herein, MCMB is an abbreviation for mesocarbonmicrobeads.

Example 7

Capacity retention profiles of MCMB/LiFePO₄ cell containing 0.1 M1,4-Bis(2-methoxyethoxy)-2,5-di-tert-butyl-benzene in 1.2M LiPF₆ inEC/EMC (3:7 by weight) were recorded over the course of 0 h to 3100 h.See FIG. 5. The charging rate was at C/10 and the overcharge is 100%.After one hundred overcharge cycles, the discharge capacities of thetest cells decreased by approximately 30%. It is believed that the highvoltage overcharge tests are beyond the normal working range of thecells, thus leading to degradation.

Example 8

Voltage profiles of a LTO/LiFePO₄ cell containing 0.1 M1,4-bis(2-methoxyethoxy)-2,5-di-tert-butyl-benzene as a redox shuttle in1.2M LiPF₆ in EC/EMC (3:7 by weight) were recorded over the course of 0h to 3100 h. See FIG. 6. The charging rate was at C/10 and theovercharge is 100%. The overcharge protection works well in full cellswith LTO as anode for more than 100 overcharge cycles. As used herein,LTO is an abbreviation for lithium titanium oxide.

Example 9

Capacity retention profiles of LTO/LiFePO₄ cell containing 0.1 M1,4-Bis(2-methoxyethoxy)-2,5-di-tert-butyl-benzene in 1.2M LiPF₆ inEC/EMC (3:7 by weight) were recorded over the course of 0 h to 3100 h.See FIG. 7. The charging rate was at C/10 and the overcharge is 100%.After one hundred overcharge cycles, the discharge capacities of thetest cells decreased by approximately 10%.

Example 10

Voltage profiles of a MCMB/LiFePO₄ cell containing 0.2 M1,4-bis(2-methoxyethoxy)-2,5-di-tert-butyl-benzene as a redox shuttle in1.2M LiPF₆ in EC/EMC (3:7 by weight) were recorded over the course of 0h to 3100 h. See FIG. 8. The charging rate was at C/10 and theovercharge is 100%. The redox shuttle shows excellent solubility incarbonate-based electrolytes, which in return benefits the overchargeperformance. The full cells containing 0.2 M redox shuttle displayedsuperior overcharge protection. Due to the relative high concentrationof redox shuttle, the cells are expected to provide thousands of hoursovercharge protection at a C/5 charging rate.

Example 11

Capacity retention profiles of MCMB/LiFePO₄ cell containing 0.2 M1,4-Bis(2-methoxyethoxy)-2,5-di-tert-butyl-benzene in 1.2M LiPF₆ inEC/EMC (3:7 by weight) were recorded over the course of 0 h to 3100 h.See FIG. 9. The charging rate was at C/10 and the overcharge is 100%.After more than 160 overcharge cycles at C/5 rate, the cells still workproperly despite the decrease in the discharge capacity.

Example 12

Voltage profiles of a MCMB/LiFePO₄ cell containing 0.4 M1,4-bis(2-methoxyethoxy)-2,5-di-tert-butyl-benzene as a redox shuttle in1.2M LiPF₆ in EC/EMC (3:7 by weight) were recorded over the course of 0h to 3100 h. See FIG. 10. The charging rate was at C/10 and theovercharge is 100%. The improved solubility of the exemplary redoxshuttle compound made it possible to use this redox compound under C/2rate. The cells containing 0.4 M current redox shuttle compound canprovide more than one thousand hours overcharge protection under a C/2rate.

Example 11

Capacity retention profiles of MCMB/LiFePO₄ cell containing 0.4 M1,4-Bis(2-methoxyethoxy)-2,5-di-tert-butyl-benzene in 1.2M LiPF₆ inEC/EMC (3:7 by weight) were recorded over the course of 0 h to 3100 h.See FIG. 11. The charging rate was at C/10 and the overcharge is 100%.After more than 180 overcharge cycles at C/2 rate, the cells still workproperly despite the decrease in the discharge capacity.

1. A compound represented by Formula I, II, or III:

wherein: R¹ is H, F, Cl, Br, CN, NO₂, alkyl, haloalkyl, phosphate, orpolyether; R² is H, F, Cl, Br, CN, NO₂, alkyl, haloalkyl, phosphate, orpolyether, or R¹ and R² join together to form a ring; R³ is H, F, Cl,Br, CN, NO₂, alkyl, haloalkyl, phosphate, or polyether; or where thecompound is represented by Formula II, R¹ and R², or R² and R³ jointogether to form a ring; R⁴ is H, F, Cl, Br, CN, NO₂, alkyl, haloalkyl,phosphate, or polyether; or R³ and R⁴ join together to form a ring; andX and Z are independently a group of Formula A:

wherein: R⁵ and R⁶ are independently H, F, Cl, Br, CN, NO₂, alkyl,haloalkyl, phosphate, or polyether; R⁷ is H, alkyl, haloalkyl,phosphate, or polyether; n is an integer from 1 to 8; m is an integerfrom 1 to 13; provided that where the compound is represented by FormulaII or III, at least one of R¹, R², R³, and R⁴ is other than H.
 2. Thecompound of claim 1, wherein R¹, R², R³, and R⁴ are independently H,alkyl, haloalkyl, or polyether.
 3. The compound of claim 1, wherein R¹,R², R³, and R⁴ are independently H, C₁-C₄ alkyl, C₁-C₄ haloalkyl, or apolyether having from 2 to 20 carbon atoms.
 4. The compound of claim 1,wherein R¹ and R⁴ are the same and are different from that of R² and R³.5. The compound of claim 1, wherein R¹ and R⁴ are individually H, alkylor haloalkyl, and R² and R³ are hydrogen.
 6. The compound of claim 1,wherein R¹ and R⁴ are individually H, methyl, ethyl, n-propyl,iso-propyl, n-butyl, sec-butyl, or tert-butyl, and R² and R³ are H. 7.The compound of claim 1 represented by Formula I.
 8. The compound ofclaim 7, wherein: R¹, R², R³, and R⁴ are independently H, C₁-C₄ alkyl,C₁-C₄ haloalkyl, or a polyether group having from 2 to 20 carbon atoms;R⁵ and R⁶ at each occurrence are individually H, a C₁-C₄ alkyl, a C₁-C₄haloalkyl, H, Cl, Br, or I; R⁷ is H or alkyl; n is 1 or 2; and m is 1 to8.
 9. The compound of claim 7, wherein: R¹, R², R³, and R⁴ areindependently H, methyl, ethyl, n-propyl, iso-propyl, n-butyl,sec-butyl, or tert-butyl, or a polyether having from 2 to 20 carbonatoms; R⁵ and R⁶ at each occurrence are individually H or methyl; R⁷ isH, methyl, ethyl, n-propyl, iso-propyl, n-butyl, sec-butyl, ortert-butyl; n is 1 or 2; and m is 1 to
 8. 10. The compound of claim 7,wherein: R¹ and R⁴ are tert-butyl; R² and R³ are H; R⁵ and R⁶ at eachoccurrence are individually H or methyl; R⁷ is H, methyl, or ethyl; n is1 or 2; and m is 1 to
 8. 11. The compound of claim 1 represented byFormula II.
 12. The compound of claim 1 represented by Formula III. 13.The compound of claim 12, wherein: R¹ and R⁴ are individually H, alkylor haloalkyl; R² and R³ are hydrogen; R⁵ and R⁶ at each occurrence areindividually H or methyl; R⁷ is H, methyl, ethyl, n-propyl, iso-propyl,n-butyl, sec-butyl, or tert-butyl; n is 1 or 2; m is 1 to
 8. 14. Thecompound of claim 12, wherein: R¹ and R⁴ are tert-butyl; R² and R³ areH; R⁵ and R⁶ at each occurrence are individually H or methyl; R⁷ is H,methyl, or ethyl; n is 1 or 2; and m is 1 to
 8. 15. The compound ofclaim 1, wherein R⁵ and R⁶ at each occurrence are individually H, aC₁-C₄ alkyl, a C₁-C₄ haloalkyl, H, Cl, Br, or I.
 16. The compound ofclaim 1, wherein R⁷ is H or C₁-C₄ alkyl.
 17. The compound of claim 1,wherein the compound is 1-nitro-3-tert-butyl-2,5-di-oligo(ethyleneglycol)benzene; 1-cyano-3-tert-butyl-2,5-di-oligo(ethyleneglycol)benzene; 1,4-di-tert-butyl-2,3-di-oligo(ethylene glycol)benzene;5-tert-butyl-1,3-dinitro-2,4-di-oligo(ethylene glycol)benzene;1-(benzyloxy)-4-bromo-2,3-di-oligo(ethylene glycol)benzene;1,3,5-tri-tert-butyl-2,4-di-oligo(ethylene glycol)benzene;2-methyl-1,4-di-oligo(ethylene glycol)benzene;2,3-dimethyl-1,4-di-oligo(ethylene glycol)benzene;2,5-dimethyl-1,4-di-oligo(ethylene glycol)benzene;2,6-dimethyl-1,4-di-oligo(ethylene glycol)benzene;2,3,6-trimethyl-1,2-di-oligo(ethylene glycol)benzene;2,3,5,6-tetramethyl-1,4-di-oligo(ethylene glycol)benzene;4-methyl-1,2-di-oligo(ethylene glycol)benzene;2,3,5,6-tetramethyl-1,4-di-oligo(ethylene glycol)benzene;2-ethyl-1,4-di-oligo(ethylene glycol)benzene;2,3-diethyl-1,4-di-oligo(ethylene glycol)benzene;2,5-diethyl-1,4-di-oligo(ethylene glycol)benzene;2,6-diethyl-1,4-di-oligo(ethylene glycol)benzene;2,3,6-triethyl-1,2-di-oligo(ethylene glycol)benzene;2,3,5,6-tetraethyl-1,4-di-oligo(ethylene glycol)benzene;4-ethyl-1,2-di-oligo(ethylene glycol)benzene;2,5-diisopropyl-1,4-di-oligo(ethylene glycol)benzene;2-tert-butyl-1,4-di-oligo(ethylene glycol)benzene;2,3-di-tert-butyl-1,4-di-oligo(ethylene glycol)benzene;2,5-di-tert-butyl-1,4-di-oligo(ethylene glycol)benzene;2,5-di-tert-pentyl-1,4-di-oligo(ethylene glycol)benzene;2,5-di-tert-butyl-3,6-di-nitro-1,4-di-oligo(ethylene glycol)benzene;2,5-di-tert-butyl-3,6-di-cyano-1,4-di-oligo(ethylene glycol)benzene;2,5-di-tert-butyl-1,4-di-oligo(ethylene glycol)benzene;2,5-dicyclohexyl-1,4-di-oligo(ethylene glycol)benzene;4-tert-butyl-1,2-di-oligo(ethylene glycol)benzene;4,5-di-tert-butyl-1,2-di-oligo(ethylene glycol)benzene;4,5-di-tert-pentyl-1,2-di-oligo(ethylene glycol)benzene;4,5-di-tert-butyl-1,2-diethoxybenzene; 9,10-di-oligo(ethyleneglycol)-1,4:5,8-dimethano-1,2,3,4,5,6,7,8-octahydroanthracene;9,10-di-oligo(ethyleneglycol)-1,4:5,8-diethano-1,2,3,4,5,6,7,8-octahydroanthracene;1,4-bis(2-methoxy)ethoxy-2,5-di-tert-butyl-benzene;1,4-bis(2-(2-methoxy)ethoxy)ethoxy-2,5-di-tert-butyl-benzene;1,4-bis(2-(2-(2-methoxy)ethoxy)ethoxy)ethoxy-2,5-di-tert-butyl-benzene;or1,4-bis(2-(2-(2-(2-methoxy)ethoxy)ethoxy)ethoxy)ethoxy-2,5-di-tert-butyl-benzene.18. The compound of claim 1, wherein the compound is1,4-bis(2-methoxy)ethoxy-2,5-di-tert-butyl-benzene;1,4-bis(2-(2-methoxy)ethoxy)ethoxy-2,5-di-tert-butyl-benzene;1,4-bis(2-(2-(2-methoxy)ethoxy)ethoxy)ethoxy-2,5-di-tert-butyl-benzene;or1,4-bis(2-(2-(2-(2-methoxy)ethoxy)ethoxy)ethoxy)ethoxy-2,5-di-tert-butyl-benzene.19. An electrolyte comprising: an alkali metal salt; a polar aproticsolvent; and a redox shuttle comprising a compound represented byFormula I, II, or III:

wherein: R¹ is H, F, Cl, Br, CN, NO₂, alkyl, haloalkyl, phosphate, orpolyether; R² is H, F, Cl, Br, CN, NO₂, alkyl, haloalkyl, phosphate, orpolyether, or R¹ and R² join together to form a ring; R³ is H, F, Cl,Br, CN, NO₂, alkyl, haloalkyl, phosphate, or polyether; or where thecompound is represented by Formula II, R¹ and R², or R² and R³ jointogether to form a ring; R⁴ is H, F, Cl, Br, CN, NO₂, alkyl, haloalkyl,phosphate, or polyether; or R³ and R⁴ join together to form a ring; andX and Z are independently a group of Formula A:

wherein: R⁵ and R⁶ are independently H, F, Cl, Br, CN, NO₂, alkyl,haloalkyl, phosphate, or polyether; R⁷ is H, alkyl, haloalkyl,phosphate, or polyether; n is an integer from 1 to 8; m is an integerfrom 1 to 13; and wherein the electrolyte solution is substantiallynon-aqueous.
 20. An electrochemical device comprising a cathode ananode; and a substantially non-aqueous electrolyte comprising: an alkalimetal salt; a polar aprotic solvent; and a compound represented byFormula I, II, or III; wherein: Formula I, II, and III are:

R¹ is H, F, Cl, Br, CN, NO₂, alkyl, haloalkyl, phosphate, or polyether;R² is H, F, Cl, Br, CN, NO₂, alkyl, haloalkyl, phosphate, or polyether,or R¹ and R² join together to form a ring; R³ is H, F, Cl, Br, CN, NO₂,alkyl, haloalkyl, phosphate, or polyether; or where the compound isrepresented by Formula II, R¹ and R², or R² and R³ join together to forma ring; R⁴ is H, F, Cl, Br, CN, NO₂, alkyl, haloalkyl, phosphate, orpolyether; or R³ and R⁴ join together to form a ring; and X and Z areindependently a group of Formula A:

R⁵ and R⁶ are independently H, F, Cl, Br, CN, NO₂, alkyl, haloalkyl,phosphate, or polyether; R⁷ is H, alkyl, haloalkyl, phosphate, orpolyether; n is an integer from 1 to 8; and m is an integer from 1 to13.